This application is concerned with visual development in human infants between 3 and 7 months of age. Our primary objective is to study the early developement of event perception, a topic concerned with the perception of invariants that unfold over time as well as space. In the current adult literature, our knowledge about event perception derives primarily from the study of motion perception, where the goal has been to describe the invariant structure in motion to which adults are senstive. In an effort to understand how infants' senstivitiy to structure in motion changes age, our research program is organized into two sets of related experiments. Five experiments are proposed to examine the infant's sensitivity to the structure of human form as presented in video displays of point-lights moving as if attached to the joints of a person walking -- an event found to be rich in structural information for adults. The second series of 6 experiments is designed to extend the center of moment concept, developed by Proffitt and Cutting, to understanding infants' perceptual organization of motion information. Specific studies will examine simple rotational motions, flow-fields, motion produced texture occlusions, and revolving subjective contours. Both series of experiments are designed to provide precise mathematical specifications of the structure perceived by infants across the 3 to 7 month age range. The technique used is a variation of the infant-control habituation procedure; visual fixation and sometimes heart rate will be used as convergent response measures. By analyzing infants' changes in responsiveness as a function of the sustematic manipulation of the stimulus events, inferences can be drawn that will contribute to our understanding of infant visual organization. Overall, we anticipate that infants will show both a high degree of sensitivity to kinematic structure as well as developmental changes in this sensitivity.